Active driver assistance systems or safety systems (PSS, Predictive Safety System), which autonomously brake vehicles in dangerous situations with the aid of radar and/or video sensor systems, have come into widespread use. However, such systems do not know whether a potentially dangerous situation is caused by the alertness of the driver. These systems therefore always constitute a compromise between a benefit and a faulty warning. For example, the benefit may possibly have to be reduced in order to prevent premature warnings of attentive drivers. Faulty warnings, on the other hand, must be accepted, so that a timely warning can be given to a driver whose attention is wandering just then.
Such systems therefore make it necessary to collect as much information as possible with regard to the current alertness of the driver in order to point out or react to dangerous situations in a timely yet not premature manner. Current systems infer the alertness of the vehicle driver from vehicle parameters or from the driving behavior.